Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in CPP):

Solution:
#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0;i < (n);i++)
using namespace std;
using ll = long long;
const ll INF = 1LL << 60;

int main(){
	int h,w;
	cin >> h >> w;
	vector<vector<char>> grid(h,vector<char>(w));
	int cnt_black = 0;
	rep(i,h) rep(j,w){
		cin >> grid[i][j];
		if(grid[i][j] == '#') cnt_black++;
	}
	
	vector<int> dy = {0,1,0,-1};
	vector<int> dx = {1,0,-1,0};
	vector<vector<ll>> d(h,vector<ll>(w,INF));
	queue<pair<int,int>> q;
	q.push(make_pair(0,0));
	while(!q.empty()){
		int y = q.front().first, x = q.front().second;
		rep(i,4){
			int ny = y+dy[i], nx = x+dx[i];
			if(ny < 0 || ny > h-1 || nx < 0 || nx > w-1)
				continue;
			if(grid[ny][nx] == '.' && d[ny][nx] == INF){
				d[ny][nx] = d[y][x]+1;
				q.push(make_pair(ny,nx));
			}
		}
		q.pop();
	}

	if(d[h-1][w-1] == INF){
		cout << -1 << endl;
		return 0;
	}
	int ans = h*w - cnt_black - (d[h-1][w-1]+1);
	cout << ans << endl;
}